Core drilling system



Aug 25, 1969 1...). MARTINSEN ET AL 3,463,255

CORE DRILLING SYSTEM Original Filed April 14. 1967 NS E mm SI TT RA n TAM HL m m w T ET A um T s United States Patent O 3,463,255 CORE DRlLLING SYSTEM Lyle J. Martinsen, Murray, Utah, and Stanton L. Matthews, Phoenix, Ariz., assignors to Boyles Bros. Drilling Company, Salt Lake City, Utah Original application Apr. 14, 1967, Ser. No. 630,907. Divided and this application Aug. 23, 1968, Ser. No. 754,886

Int. Cl. EZlb 9/20 U.S. Cl. 175--244 1 Claim ABSTRACT OF THE DISCLGSURE In a core drilling system, an inner tube having a minute interior taper converging toward the core-receiving opening of a core barrel assembly to enhance 1) the core displacement into the inner tube during drilling and (2) subsequent removal of the core from the inner tube.

The present invention relates generally to the core drilling art and more particularly to novel core barrel structure which provides for more efficient core barrel operation, longer expected core barrel life, and longer periods of uninterrupted use of the core barrel and which includes a novel inner core-receiving tube having a minute downwardly converging interior taper. This application is a division of U.S. patent application Ser. No. 630,907, filed Apr. 14, 1967.

In core drilling, it has been customary to employ an annular drilling bit disposed at the distal end of an outer tube comprising the distal end of a drill string. The bit progressively cuts through rock responsive to rotation f the drill string, leaving an uncut upwardly-projecting rock core central of the bit. As drilling proceeds, the core incrementally becomes disposed within a core-receiving barrel or inner tube of a core barrel assembly, which is positioned inside the drill string so as to be releasably coupled with the outer tube by a latching assembly of the core barrel assembly. A `swivel mechanism is interposed between the core-receiving barrel and the core barrel latching assembly so that the Alatching assembly rotates rwith the drill string and the core-receiving barrel is normally stationary during drilling.

As drilling takes place, water is continually pumped along the periphery of the core barrel assembly outward around the drilling bit and upward along the exterior of the outer tube to the surface, thus cooling the bit. The long column of Water exerts very high hydrostatic and hydrodynamic pressures in the drill hole.

When a length of core has been disposed in the corereceiving barrel suicient to till the barrel (usually several feet long), the drill string and/or the core barrel is displaced a short distance away from the leading end of the hole adequate to break the core from the rock formation. An overshot, carried at the end of a wire line (cable), is latched to the latching assembly of the core barrel assembly, the core barrel assembly is uncoupled from the outer tube and the overshot and latched core barrel assembly with the broken core therein are withdrawn to the surface.

Although core drilling beneath the surface of the earth has been practiced for many years, a number of very onerous problems have persisted in the art. For example, using prior techniques, the core, during drilling, tends to frictionally bind or jam up against the inside cylindrical surface of the inner tube as the inner tube progressively descends over the core during drilling. This frequently distates that drilling be suspended at points in time when only a fraction of the inner tube is iilled with core so that the core barrel assembly can be elevated to the surface and the jammed core removed. Thus, comice monly, the amount of time and labor spent to actually drill is small by comparison to the time and labor spent in transporting the core barrel assembly to and from the surface and in removing the core from the inner tube at the surface. From time to time the core will become so tightly frozen in the inner tube that it becomes more practical to replace the inner tube than to remove the core.

With the foregoing in mind, the present invention has as its primary object the provision of a novel core-receiving or inner tube comprising part of a core barrel assembly, for the alleviation of the above-mentioned problems.

More specifically, the core barrel assembly of this invention provides a novel inner tube fabricated to have a Aminute divergent taper away from the opening at the distal end of the inner tube throughout essentially the entire length of the inner tube, which accommodates comparatively easily placement in and removal of the core from the inner tube.

Accordingly, it is an additional important object of this invention to provide an inner tube having a very slight interior taper for easier acceptance and removal of the core and for increasing the likelihood that the inner tube will be essentially lled with core during each drilling cycle so that down time will be significantly reduced.

The foregoing objects and features of the presents invention will become more fully apparent from the following description and appended claims taken in conjunction with the accompanying drawings wherein:

FIGURE 1 is a vertical cross-section of the present novel core-receiving or inner tube comprising the lower part of a core barrel assembly.

Reference is now made to FIGURE l which fragrneutarily depicts a core drilling apparatus constructed according to the present invention and generally designated 20. The core drilling system 20, as is conventional, comprises an outer tube 22, disposed at the distal end of a drill string (not shown). A depending distal bit 24 is threadedly joined at 25 to the outer tube 22 and is positioned along with the drill string in a downwardly-extending hole 26 in a rock formation 27 in the earth.

During drilling, as is also conventional, the drill string along with the outer tube 22 and the bit 24 are rotated by conventional apparatus (not shown) causing the bit to progressively cut an annular hole in the rock formation 27, leaving an uncut rock core 36 within the hollow of the bit, which core incrementally increases in length as drilling proceeds.

As the core barrel assembly (not fully shown) progressively descends, as is conventional, over the rock core 36 during drilling, the core is accepted within a corereceiving barrel 38 of an inner tube 40 of the core barrel assembly through a conventional shoe 44 and a core spring 46.

The inner tube 40 of this invention is fabricated to maximize the probability that the inner tube Will be totally lled during each drilling cycle and thereby avoid premature retrieval of the core barrel assemble, attached to the inner tube 40 at threaded connection 50', to the surface due to jamming or the like of the core within the inner tube. In this Way, previous time and labor losses are substantially reduced. Ease of entry and subsequent of removal of the core 36 from the inner tube 40 is significantly improved by fabricating the barrel 38 of the inner tube 40 so that it has a very minute interior taper which generally diametrically converges toward the core spring 46 up to about on the order of 0.2%, i.e. up to about a maximum of one quarter inch change in radius per ten axial feet of inner tube. Not only does the core 36 enter the inner tube with surprisingly less resistance and continual relief of resistance to core displacement within the inner tube afforded, but when the core barrel assembly is elevated to the surface and the inner tube 40 Unthreaded at 50 from the remainder of the core barrel assembly, the core can be conveniently discharged from the inner tube through the proximal opening adjacent the threads at 50 in a comparatively easy, painless manner.

For a more complete discussion and disclosure of suitable core barrel assemblies which may be utilized with the present invention, the subject matter of parent U.S. patent applications Ser. No. 571,521 and Ser. No. 630,907 respectively filed Aug. 10, 1966, and Apr. 14, 1967, is hereby incorporated into this specification by reference.

From the foregoing, it should be appreciated that the novel improvement of the present invention provides a maximum likelihood that the inner tube of a core barrel assembly will be totally lled during each drilling cycle so that time and labor losses heretofore incurred, because of a need for premature retrieval of the core barrel assembly, will be minimized. At the same time, the core may be more readily removed from the inner tube at the surface.

This invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The present embodiment is, therefore, to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing ,4 description, and all changes which come within the meaning and range of equivalancy of the claims are therefore to be embraced therein.

What is claimed and desired to be secured by United States Letters Patent is:

1. In a core drilling apparatus comprising a core barrel assembly, the improvement comprising a core-receiving inner tube adapted to be disposed between a drilling bit and a swivel mechanism of the assembly, the inner tube having an interior taper, along substantially the entire length thereof, converging toward the distal end up to about on the order of 0.2% whereby resistance to progressive entry of the core into the tube is materially reduced and subsequent removal of the core from the tube is significantly eased.

References Cited UNITED STATES PATENTS DAVID H. BROWN, Primary Examiner U.S. Cl. X.R. 

